Power out to instruments

Stu Jackson · November 21, 2006, 11:42:37 AM

So, I have this friend who's too shy to post this question. He has a 10 year old Mark II. When he turns on the ignition key to start the engine, the engine starts, but then the instrument power goes out, and, I think, his fuel pump goes off, too. Since he won't write up his own question, I'm trying to remember his symptoms from a conversation the other day. I was intrigued, and wonder if you have any observations that may help him. He had an "electrician" down to the boat who couldn't figure it out, so he paid the guy, who left. Really very helpful...

Craig Illman · November 21, 2006, 11:55:27 AM

You sure it isn't a friend with a 20 year old Mark I ?

It sounds like the ignition switch itself to me.

Craig

Stu Jackson · November 21, 2006, 12:02:11 PM

Uh, Craig, good one! Nope, that's why I stuck that description in there. My 20 year old ignition switch still works, most likely because we're DIYers.

BTW, he's already done that. Any other good ideas?

I was thinking breaker (OH YEAH, I forgot to mention his breaker is popping - OK, anything more I left out?) Don't think so. Don't know which breaker, either, but I don't think it's the one on his panel, I think he said it's a separate black one with a red button. We don't have those new fangled thingies on our old boat - fuses are so old school, eh?

This is the inherent weakness of asking a question for someone else. I was also thinking he may have some crimped wiring in this binnacle that could be causing a short somewhere.

Craig Illman · November 21, 2006, 12:10:13 PM

I was going to next suggest ground, but with a breaker popping, either the breaker is bad or there's a short somewhere that with the extra voltage of a charging alternator, it trips the breaker? I'm sure Ron will come up with the obvious answer. I assume these are the engine instruments, not the depth, wind, etc. ? I replaced my engine panel about 18 months ago. Seaward put a breaker on the panel for the blower and instruments.

Craig

rirvine · November 21, 2006, 05:16:59 PM

I had a very similar problem. The circuit breaking in the engine panel would open shortly after the engine was started. It turned out be caused by the blower motor drawing more current than the rating of the CB. If the blower motor was not turned on the CB stayed closed. Taken the blower motor off the CB and give the blower its own fuse.

Ray

Ron Hill · November 21, 2006, 05:59:28 PM

Stu : The obvious question is "which breaker". As I recall the MK II has a breaker on the engine instrument panel and a breaker on the engine that controls the glow plugs and the electric fuel pump ??? The oil pressure may also be involved in that wiring "lash up".
He needs to look at his wiring diagram and start checking.
Think I might run a separate hot wire (#10 or 12) from the starter solenoid to the + pole on the key switch (after disconnecting the old one) and see what happens.

Stu Jackson · November 22, 2006, 11:42:37 AM

Here are some more symptoms for you detectives:

fuel breaker keeps popping and there are some accompanying consequences -- tach goes to 3000rpm, the voltmeter at the helm drops to 0, and the voltmeter on the electrical panel "spikes."

rirvine · November 22, 2006, 11:55:47 AM

Stu:

Could you define "fuel breaker" - do you mean the breaker on the back of the engine?

Does the breaker stay closed when the engine is not running?

When the key is "on"? When the key is "off"? When the glow plugs are "on"? When the glow plug is "off"?

How long after the engine is started, does the breaker open?

Does the Cb in the engine panel "open"? If so, when in the process?

It appear to me that the next step is to find out why this CB opens - something down stream is drawing too much current

I assume this is an M35B Engine.

Jon Arck - Past C34IA Commodore · November 22, 2006, 06:34:51 PM

Hi, Everyone

Okay, Stu wrote the post for me because I was going to solve the problem (which I thought would be easier than it's been), then write about it. Shy I'm not...

The breaker mounted on the M35B engine next to the fuel pump used to pop after about 1/2 hour; now it pops as soon as the engine is started -- even when the exhaust fan is off. While the engine pod instrument pods go off, the engine keeps running. If the key is turned on without starting the engine, the breaker stays closed.

Resetting the breaker enables the engine to be started again (and the engine pod instruments work). Then, the breaker pops again as soon as the engine is started.

The breaker in the engine pod doesn't pop. The Navod instruments aren't affected.

So far, we replaced the ignition switch and starter button, cleaned/sealed all the wires on the bussbar and checked all connections in the engine pod and the electrical panel at the nav station. We checked the engine ground and the alternator output, as well as the tach output.

At Stu's suggestion, we'll wire a new 20 amp breaker in parallel with the current one and see whether the current one pops while the new one stays closed. If we still have a problem, we'll try Ron's suggestion. As soon as we try it/them, I'll post another message. Regardless, I like Ray's suggestion of a separate fuse for the exhaust.

Thanks to everyone for your comments/suggestions.

Mike and Joanne Stimmler · November 23, 2006, 02:56:38 PM

Jon,
One question. Was any work done on your boat previous to your problem starting?

Mike

sedelange · November 23, 2006, 04:51:20 PM

Have you considered wiring an ammeter in the circuit to measure the actual current? Shotgunning parts is an expensive solution.

Sailing Steve · November 23, 2006, 10:37:16 PM

Jon, I could be off, but if you wire a second 20 A circuit breaker in parallel with the first as you've suggested, in theory you now have a potential 40 A breaker, do you not? If this is correct and there is a fault in the circuit, you may end up with some real damage.

I would suggest that if you don't have the ammeter as suggested in the previous post, and you're going to buy a second 20 A breaker, replace the existing breaker with the new one.

If you want to do a comparison of the old vs. new breaker without the risk of a potential short circuit damaging your wiring, you could wire the two breakers in series. Then either one could trip at or below their rated 20 A, and see if the old one constantly trips first.

My $0.02

Ken Juul · November 24, 2006, 06:50:40 AM

CB sometimes pop because of heat build up rather than overload. Once you install a new CB, most stores won't take it back. I would just install a new one. If the problem goes away the orig CB is bad, if it doesn't then the orig CB is ok, you now have a spare.

Jon Arck - Past C34IA Commodore · November 26, 2006, 12:09:12 PM

Hi, Everyone

The last work done was to install a ST4000+ autopilot about two years ago, besides adding engine compartment insulation in the spring/summer (which could cause heat buildup, and I'll check).

TransPacific, the local distributor, suggests that I check the batteries for a short (especially since the pair of American Battery 4Ds are 7 years old), so I'll do that tomorrow and see if that's the problem. Stay tuned...

Thanks and Happy Thanksgiving to everyone,
Jon